1. Field of the Invention
The invention relates to the process and apparatus for determining the amount of dispersed water-immiscible solid organic substances in sewage water and somewhat more particularly to a computer-controlled analysis system for accomplishing the foregoing.
2. Prior Art
Analysis of the amount of organic substances contained or dispersed in sewage water or the like is useful for determining the parameters needed for purification or other treatment of such water as well as in determining, for example, the efficiency of the overall sewage system. However, such analysis is rather costly because of the multitude of process steps and individual operation required in accomplishing such analysis. In a typical prior art process, a technician obtains a defined amount of sewage water from a given source thereof, admixes such water with precise amounts of various reagent solutions, including sulfuric acid and silver sulfate to prepare the sewage sample suitable for analysis of the quantity of organic substance therein. Next, the technician admixes the prepared sewage sample with a potassium dichromate, (K.sub.2 Cr.sub.2 O.sub.7), solution and heats the resultant solution close to the boiling point thereof for a period of time sufficient for the oxygen, released from the potassium dichromate solution during the reduction of Cr.sup.+6 -ions into Cr.sup.+3 -ions, to completely oxidize the organic substance. Then the technician determines the residual amount of Cr.sup.+6 -ions in the resultant solution by titrating with a Fe.sup.+2 -ion containing solution so that a reaction in accordance with the following formula scheme takes place: EQU Cr.sub.2 O.sub.7.sup.-2 +6Fe.sup.+2 +14H.sup.+ .fwdarw.2Cr.sup.+3 +6Fe.sup.+3 +7H.sub.2 O
The technician then notes the amount of consumed Fe.sup.+2 -ion containing solution and converts such indirect measure into the amount of organic substance contained in the sewage sample. The foregoing procedure can only be practically carried out in a laboratory setup wherein a given water or sewage sample defined in terms of its volume, must first be subjected to a pretreatment to prepare it for an orderly analysis. As is known, a wide variety of substances can be found in water or sewage which interfere with an orderly analysis of organic materials therein in accordance with the above described, analytical procedure. Thus, chlorides typically present in water interfere with the above described analysis. In order to mask the free chlorine ions contained in sewage water or the like, a mercury sulfuric acid solution is intimately admixed with the sewage sample before such sample is subjected to analysis. Even in a potassium dichromate solution used as an oxidizing reagent wherein chromium exists as a 6.sup.+ -valent ion, in combination with the distilled water, there is a tendency toward reduction of chromium to a 3.sup.+ -valent ion and this fact must be taken into account during the aforesaid analysis. Further, the Fe.sup.+2 -ion containing solution used for titrating the reacted sewage-reagent solution, is not chemically very stable because the Fe.sup.+2 -ions endeavor to transform themselves into the more stable Fe.sup.+3 -ions. It is therefore necessary for the analytical technician to precisely determine the amount of Fe.sup.+2 -ions in the titration solution which, incidently, also contains Fe.sup.+3 -ions therein, before beginning the titration procedure. In addition, titrating the reacted sewage-reactant solution with this iron solution is difficult as the end point of the titration, i.e., that point at which all of the Cr.sup.+6 -ions still present in the reacted sewage-reagent solution are reduced to Cr.sup.+3 -ions, is only imprecisely determinable with traditional techinques.
The aforementioned problems do not allow this analysis procedure to be materially accelerated or to be automated, which would be highly desirable.